from multiprocessing import Pool
import os, time, random

def long_time_task(name):
    print('Run task %s (%s)' %(name, os.getpid()))
    start = time.time()
    time.sleep(random.random() * 3)
    end = time.time()
    print('Task %s runs %0.2f seconds.' %(name, (end - start)))

if __name__ == '__main__':
    print('Parent Process is %s.' %(os.getpid()))
    p = Pool(4)
    for i in range(5):
        p.apply_async(long_time_task, args=(i,))
    print('Waiting for all subprocess done..')
    p.close()
    p.join()
    print('All subprocess done..')